EXPERIENCING THE ECLIPSE​The Sight of a LifetimeAugust 21st, 2017, will mark the first time this century, and the first time since 1979, that a total solar eclipse will cross the contiguous (lower 48) United States (Alaska had its turn in 1990; Hawaii in 1991). And for the very first time, the shadow track — better known as the “path of totality” — will sweep only over the United States and no other country.Many Americans taking full advantage of this event’s close proximity to their homes will have a golden opportunity to witness firsthand one of the most beautiful and most exciting of nature’s sky events. The total eclipse will be seen by an estimated 12 million people who fortuitously live within the totality path. However, the number of people who are within just one day’s drive of the totality zone is probably around 200 million.Not since 1970 has there been an opportunity to see a total solar eclipse in such easily accessible and widespread areas of the United States. There have been a couple of limited opportunities, such as in 1972 (Quebec and the adjacent Canadian Maritime Provinces) and 1979 (the Pacific Northwest and Northern Plains), but the areas of visibility were either limited or somewhat difficult to reach. And not until April 2024 will there be another opportunity comparable to that offered on Aug. 21, 2017.

From Coast to CoastAlso, for the first time since 1918, the moon’s dark shadow will sweep across the U.S. from coast to coast. At local sunrise on this third Monday in August, the shadow of the moon will first touch the Earth at a point in the North Pacific Ocean, about 1,500 miles (2,414 km) northwest of the Hawaiian Islands. Then, for 3 hours and 13 minutes, the shadow will race first east-northeast, then east and finally southeast, along the way darkening a narrow strip of the North American continent.Initially, the shadow will traverse nothing but wide-open ocean for 28 minutes. Finally, it will make landfall along the coast of Oregon at the community of Lincoln Beach.Traversing the United States, the total eclipse will be visible within a path of darkness stretching from Oregon and then on through Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina and, finally, South Carolina.The path will average 67 miles (108 km) in width, but while moving through western Kentucky, about 12 miles (19 km) northwest of the town of Hopkinsville, the shadow’s size will widen to a maximum of 71 miles (114 km).

Experiencing TotalityBecause the moon’s shadow is moving at such a tremendous speed, totality cannot last very long in any one place. The duration of the total phase is always longest along the center of the shadow’s path. As an observer moves away from the center, the duration of totality time decreases, becoming zero along the path’s edges.Right at the Oregon coastline, totality lasts 1 minute and 59 seconds, as the shadow will be traveling at more than three times the speed of sound (2,400 mph, or 3,900 km/h). Heading southeast along the center line, the totality time slowly lengthens, reaching a maximum of 2 minutes and 40.3 seconds at a spot in southern Illinois about a dozen miles (about 20 km) southeast of the city of Carbondale.The shadow — which, at this point, has slowed to 1,450 mph (2,330 km/h) — then begins to increase in speed, and the duration of totality subsequently begins to diminish. Indeed, when it arrives at the South Carolina coastline, the duration of totality will have dropped to 2 minutes and 34 seconds. The shadow then exits out to sea, finally leaving the Earth 75 minutes later at local sunset in the North Atlantic Ocean, 390 miles (627 km) to the southwest of the island nation of Cape Verde.Notable cities inside the totality path include: Idaho Falls, Idaho; Casper, Wyoming; Grand Island, Nebraska; Lincoln, Nebraska; Columbia, Missouri; Nashville, Tennessee; Columbia, South Carolina; and Charleston, South Carolina. The metropolitan areas of Kansas City, Missouri, and St. Louis are right on the edge of the totality path.All of North America will be inside the penumbra, causing a rather large partial eclipse for much of the U.S. and portions of southwest Canada. The closer you station yourself to the path of totality, the greater the magnitude of the partial eclipse will be. When watching the partial phases, observers should take precautions while viewing the still blindingly bright sun.As you prepare for 2017 total solar eclipse here in the United States, take this opportunity to learn more about what causes eclipses, what to expect during an eclipse, as well as learn about how to safely view an eclipse.